How to implement guide with fastapi and pydantic validation for nested data models in python 3.11
I've been working on this all day and I'm working with an scenario while using FastAPI with Pydantic for data validation... I have a nested data model that includes a list of items, but I'm getting a validation behavior when the input data has the wrong structure. Here’s the relevant model definition: ```python from pydantic import BaseModel, conlist class Item(BaseModel): name: str quantity: int class Order(BaseModel): items: conlist(Item, min_items=1) ``` When I try to send a request with the following payload: ```json { "items": [ { "name": "apple", "quantity": 2 }, { "name": "banana" } ] } ``` I receive the following validation behavior: ``` ValidationError: 1 validation behavior for Order items -> 1 field required (type=value_error.missing) ``` It seems like Pydantic is expecting both the `name` and `quantity` fields for every item in the list, but I only provided `name` for the second item. I thought that Pydantic would just skip over missing fields if they were optional, but it seems that's not the case here. I tried changing the `quantity` field to `Optional[int]`, but that leads to a different behavior. What's the best way to handle optional fields in a nested model like this in FastAPI with Pydantic? Am I missing something in my model definition? Any advice would be greatly appreciated. I'm working on a web app that needs to handle this. The project is a desktop app built with Python. Thanks for any help you can provide!